Metallic or metal-coated articles, such as metallized glass fibers, are incorporated into plastic laminates to dissipate electrostatic charge and to provide shielding against electromagnetic radiation, among other benefits. These properties depend on the electrical conductivity of the metallic articles. The most common methods of making such laminates involve using metal-coated fibers which have been cut into relatively short lengths of about one-half to one inch or even shorter. The electrical properties of such laminates rely on effective metal-to-metal contact between the short lengths of metallized fiber. At high frequencies, capacitative or inductive effects between adjacent fibers may reduce the importance of metal-to-metal contact.
In making the laminates, the short lengths of metal-coated fiber are combined in with fluid polymerizable material which becomes the plastic matrix. In the fabrication of the laminate, the many individual lengths of metallized fiber develop a thin film of the insulating plastic, perhaps as thin as a few hundred-thousandths of an inch, at the point of contact with adjacent metal-coated fibers. This thin insulating film reduces or destroys the electrical conductivity at the fiber junction points. Since the metal-coated fibers in the finished laminate take the form of a three-dimensional network, there is a myriad of potential parallel paths for the flow of electric current. The conductivity of the laminate is the combined effect of the conductivity of the many individual current paths.